According to the prior art, a sealing film usually has a tab extending therefrom such that a user can grip the tab in order to tear off the sealing film. However, the outwardly extending tab is typically too tiny for an average user to grip firmly.
Furthermore, according to the prior art, the junction of the sealing film and the tab extending therefrom is seldom structurally durable and thus is likely to sever under a pull applied by a user.
During a process whereby the mouth of a container is being sealed with the sealing film, the tab has to be folded. However, the tab thus folded is not flush with the sealing film. As a result, the tab-disposed portion of the sealing film cannot seal the mouth of the contain tightly, thereby resulting in the likelihood that the contents of the container may leak out of the container.
To overcome the aforesaid drawbacks of the prior art, a hidden tab structure was put forth. However, the hidden tab structure has its own drawbacks too. For example, the hidden tab structure is made of a foam material which is too adhesive to operate. Furthermore, the hidden tab structure is made of various materials of different coefficients of thermal expansion, and the difference between the coefficients of thermal expansion account for warps that arise from heat treatment.